A number of different techniques have been developed and used for converting solid chemicals used in cleaning processes into a concentrated solution. For example, devices designed for a powdered, flaked or granular detergent are disclosed in Daley et al, U.S. Pat. No. 3,595,438, issued Jul. 27, 1991; Moffet et al, U.S. Pat. No. 4,020,865, issued May 3, 1977; and Larson et al, U.S. Pat. No. 4,063,663, issued Dec. 20, 1977. Another form of solid detergent is the pre-shaped detergent briquette. Dispensing systems for dissolving detergent briquettes are known in the art. See, for example, U.S. Pat. Nos. 2,382,163; 2,382,164; and 2,382,165 all issued Aug. 14, 1945 to MacMahon; and U.S. Pat. No. 2,412,819, issued Dec. 17, 1946 to MacMahon.
A more recent form of solid detergent is the "cast" or block form. The detergent block may comprise a detergent cast within a mold or container or a detergent block which is free-standing. Dispensing systems for these solids are known in the art. See, for example, U.S. Pat. No. 4,426,362, issued to Copeland et al and commonly owned U.S. Pat. Nos. 4,569,781 and 4,569,780, issued Feb. 11, 1986, to Fernholz et al. The cast detergent is dispensed by spraying a solvent onto the detergent block within the container, thereby dissolving the exposed surface of the detergent to form a concentrated working solution. The concentrated working solution falls into a reservoir or is directed by a conduit to the wash tank of a washing apparatus. When the chemical compound within the container is completely utilized, the exhausted container may be simply discarded and a fully charged container may be placed in the dispenser.
Solid, cast chemicals used in cleaning processes are preferably cast in a sturdy container which can act as a mold, a shipping and storage container, and a dispenser housing. The cast chemical may be dispensed by inverting the container over a spray nozzle and impinging solvent directly onto the exposed surface or surfaces of the chemical contained therein. The container may either be retained within the dispenser as the chemical is being used, or the chemical may be removed from the container and placed into the dispenser. However, hazardous chemicals used in cleaning processes such as highly alkaline detergents are preferably packaged such that they can be dispensed without coming into physical contact with the human body.
Known dispensing devices have sought to maintain a relatively constant rate of the chemical being dispensed, or a constant concentration, by maintaining a fixed distance between the dissolving spray nozzle and the exposed and erodible surface of the solid block of chemical. See, for example, commonly owned U.S. Pat. No. 4,687,121, issued to Copeland on Aug. 18, 1987; U.S. Pat. No. 4,690,305, issued to Copeland on Sep. 1, 1987, and U.S. Pat. No. 4,826,661, issued to Copeland et al May 2, 1988. Alternatively, a separate control system has regulated the amount of detergent dispensed and has maintained a constant concentration, thereby making it unnecessary to control the nozzle-to-eroding surface distance.
In many situations, however, it is desirable for the chemical concentration to be variable. The optimum chemical concentration depends upon such factors as the type of solid chemical being dispensed, the type of surface being cleaned, the amount of soil being removed from the fabric or surface being cleaned, the temperature of the solvent, the degree of mechanical action applied to the fabric or surface being cleaned, and the volume of cleaning solution being produced.
In the past, adjusting the concentration of the cleaning solution has typically been done manually by the operator. That is, a certain amount of cleaning solution has been dispensed from the solid chemical, to which a certain amount of water is added. If a higher use solution concentration is desired, then less water is added to the concentrated cleaning solution. However, this procedure does not result in a consistent, precise, and controlled solution concentration, and often results in the use solution having either too much or too little cleaning chemical concentration.
Accordingly, a need exists for a dispensing apparatus which can simply, safely, efficiently and inexpensively dispense a concentrated chemical solution from a solid block of wash chemical at predictably variable and adjustable concentrations.